Bimetallic or multilayer casts, which are cast from two or more different metallic materials, e.g. of various alloys, namely so that two or more materials are poured into one and the same mould. At first the first material is poured, which creates the first layer of the cast and after a certain dwell into the same mould the second material is poured, which creates the second layer, possibly analogically into the same mould after a further with a dwell is poured another material, which creates further layer of the cast, etc. Absolutely necessary condition for creating a high quality bimetallic or multilayer cast is achieving of a perfect diffusion joining of individual layers of the cast on the boundary of contact of individual layers. For a perfect diffusion joining of individual layers being cast with a mutual time delay, it is necessary to secure, that on the solidified, but still hot surface of the first layer, are present no oxides or oxide films at the moment of pouring the second material into the mould, or that these oxides or oxide films are not created in the fluid metal during its streaming through the sprue system and the cavity of the mould during pouring of the second material. There are known several solutions for elimination or reduction in occurrence of these oxides or oxide films.
DE 101 13 962 discloses a casting method for production of metallic parts consisting of at least two different materials, at the same time the one is a steel-based and the second is an aluminium-based. This method comprises the steps of applying of metal layer preferably on the body from the steel-based material, at the same time the metal layer is preferably the aluminium-based one, and inserting of such coated body into the casting mould before it is poured by aluminium. Before aluminium is poured, a liquid means is brought on the aluminium layer formed on surface of the steel body, which causes reduction, possibly removal, of oxygenated coating created on the metal layer, and the aluminium-based casting material upon pouring creates a metallurgic joining with metal layer. The liquid means is formed of eutectic composition consisting of K3AIF6 and KAIF4.
EP 348 300 discloses production method of parts from polymetallic composite by means of bottom casting. The part comprises at least two layers from different metal materials. Insertion covered by a layer of paraffin is hung into an ingot-mould, which by its shape corresponds to the contour of the insertion, from bottom the ingot-mould is filled with metal of a specified temperature and in a specified speed so that the metal totally floods the insertion and it produces a polymetallic ingot, which after then is hot rolled or cold rolled.
EP 1 462 194 discloses a production method of metal parts comprising at least two different materials, out of which one is on basis of a steel alloy and the second is on basis of aluminium alloy. At this method, firstly is on the body of steel based alloy created a metal layer on aluminium basis, preferably on Al—Si or FE basis. Subsequently, on such created metal layer is applied a silicone powder and/or borax (Na2B4O7-10H2O, hydrated sodium borate). After then, in such a manner coated body is positioned into the casting mould and an aluminium based alloy is poured on it.
JP 58032543, JP 1066061 and JP 7308742 disclose various applications of inert gas Ar (Argon) either in principle in a pure form, or in a mixture with 2% to 8% of hydrogen to create and maintain a non-oxidizing atmosphere in the space of future metallurgic joint of layers of various metals in one resulting metal part.
The common disadvantage of the known background art is a limited efficiency in elimination of occurrence of oxides and oxide layers.
The goal of the invention especially is to achieve a higher efficiency in elimination of undesired oxides and oxide layers, that negatively influence joining of individual layers of different materials being cast.